1. Field of the Invention
This invention relates generally to devices for the acquisition of electroencephalographic (EEG) signals, and more particularly concerns an electrode locator device that can be applied by a user without assistance for acquiring high quality EEG signals, and is comfortable and cosmetically acceptable for use during daily activities.
2. Description of Related Art
Advances in detection and characterization of electroencephalographic (EEG) signals from the brain have allowed EEG monitoring to be useful in analysis of neurological disorders, and laboratory studies of awareness and sleep. Recent advances have, for example, provided much information about the correlation between EEG signals and an individual's level of arousal, in a continuum from vigilance to drowsiness, and sleep onset. Devices for monitoring EEG signals are typically used in a laboratory environment or in a home for sleep studies, but are typically set up and operated by trained technicians. Shifts in EEG signals have been directly correlated with changes in performance, particularly during tasks which require sustained attention over prolonged periods of time. However, application of EEG monitoring to environments for study and monitoring of brain performance, such as for monitoring brain activity in the home, office, aircraft cockpit, and train or truck operations cabins, for example, has been severely hampered by cumbersome detection and recording equipment, and the need for the assistance of a technician typically required to obtain high quality data.
In fitting EEG electrodes to the scalp of a subject being monitored, an EEG technician will typically first measure the distances between the nasium and the occipital bone, and between the mastoid processes, to identify the top center (Cz) of the head, and will then position all other electrodes relative to these landmarks to comply with the International 10/20 System that is well known in the art as the standard for positioning of EEG electrodes. The technician will then part the hair of the scalp of the subject at the intended electrode sites, clean the electrode sites to remove dirt, hair oil, and the like, and prepare the scalp to remove the top layer of dead skin, to ensure that low scalp-electrode impedance values are obtained.
Conventionally, after preparation of the intended electrode sites on the scalp, electrodes are glued to the scalp with collodion, typically a viscous solution of pyroxilin, a commercially available nitrocellulose, in ether and alcohol, that is a particularly noxious preparation that can bond with the scalp and hair, to provide a stable scalp-electrode interface, until dissolved by a solvent such as acetone, or a non-acetone, oil based collodion remover.
A variety of hats, caps, helmets and headgear are known that have been developed to position EEG electrodes according to the International 10/20 System and provide a scalp-electrode interface without the use of an adhesive such as collodion. However, these types of devices are commonly uncomfortable and unacceptable for use during activities of work and daily living. One such sleep monitoring headgear utilizes a circumferential elastic headband to generate an electrode seating pressure for a single electrode located at the top center of the head of a subject. It has been found, however, that when such a circumferential elastic headband is utilized to seat multiple electrodes, the headband slides up and posteriorly on the forehead.
Such conventional hats, caps, helmets and headgear also typically make it difficult for a user to part the hair or abrade their scalp at the electrode site without assistance. Particularly where disposable electrodes are used that are not to be bonded to the scalp of the user to provide an electrode-scalp interface, the placement of an electrode over hair can increase the impedance between the electrode and scalp, causing significant signal artifacts if the hair slides or is pulled across the surface of the electrode while signals are being acquired. One such conventional device requires the technician to lift or turn a disposable electrode on its side after a conductive gel on the electrode has made contact with the hair of the scalp, in order to part the hair at the intended area of the scalp for placement of the electrode. Several systems used in the laboratory for non-ambulatory EEG monitoring dispense electrode gel to the electrode, but would make an EEG electrode locator headgear uncomfortably heavy and inconvenient for ambulatory use outside a laboratory environment. Another type of device utilizes sharp tipped metal points to penetrate the dead layer of skin. However, such sharp metal points can pose a medical danger due to the potential for infection, particularly with repeated abrasions, and the possibility of penetration of the skull if the device were to be struck accidentally during ambulatory activity, or other activities during daily living.
It would therefore be desirable to provide an EEG electrode locator headgear that utilizes electrode locators to identify electrode sites, and gives the user access for application of electrodes to the electrode sites, permitting conventional scalp preparation techniques, such as application of abrasion cream with a"Q-tip", for example, to be applied by the user without technical assistance. It would also be desirable to provide an EEG electrode locator headgear utilizing a device allowing for a user to prepare an intended electrode site on the scalp by parting of the hair, prior to seating of the electrodes, and for placement of electrodes. While prior EEG electrode locating techniques typically required a technician to accurately locate electrodes, it would be desirable to provide an EEG electrode locator headgear that utilizes a locating device that can be positioned by the user over a prominent location on the scalp of the user, such as over the occipital bone, or over the nasium, to orient the headgear and confirm accurate placement of the EEG electrodes. The present invention meets these needs.